The present invention also relates to a method for estimating a vehicle radar system misalignment, the vehicle radar system being used for detecting objects outside a vehicle. The method includes the step of detecting target angle and target Doppler velocity for each detected object during a certain time interval.
Today, a radar device may be mounted on a vehicle in order to detect reflections from objects in a traveling direction in order to implement functions of speed control and collision prevention. In such a radar device it is required to obtain an azimuth angle in the form of a target bearing angle, a distance with respect to the object and a relative speed between the vehicle and the object.
For most vehicle radar applications it is important to measure the target bearing angle with very high precision. The angle accuracy of a radar system depends on fundamental parameters like modulation technique, component tolerances, assembly precision or installation conditions. Furthermore, due to various environmental influences such as mechanical stress or bad weather, the angle estimation performance might suffer additionally. Some of those error sources show a random statistical distribution while others lead to a fixed angle offset. This fixed offset is the so called misalignment angle. Monitoring the misalignment angle is often an essential requirement in vehicle applications.
There are several approaches known which use vehicle dynamic information, e.g. vehicle speed, yaw-rate or steering angle, to verify trajectories of ground stationary targets. By comparing the expected path of an obstacle with the actual progression of the radar observations, one should be able to estimate the common bearing bias. The success of these techniques highly depends on the precisions of the vehicle dynamic data.
Addressing the above problems, the document U.S. Pat. No. 7,443,335 discloses angle error estimation for a vehicle radar based on relative speeds and reflections. However, since the required accuracy is not available without additional cost impact, it is desirable to have an alternative algorithm which doesn't need exact vehicle data.
There is thus a need for a device and a method for vehicle radar angle error estimation which does not need exact vehicle data.